ORA-28056: Writing audit records to Windows Event Log failed

Problem Description
Connecting as sysdba fails with ORA-28056.

$ sqlplus / as sysdba
ORA-28056: Writing audit records to Windows Event Log failed.

Cause of the Problem
The problem happened because Event Viewer log is full and not able to log anymore events.

Solution of the Problem
You need to free an event log.

- Log in as a administrator or a member of the Administrators group in order to free an event log.

- Open Event Viewer. To do so click on Start Menu, click Control Panel, click Performance and Maintenance, click Administrative Tools, and then double-click Event Viewer.

Or, click on Start Menu, click Control Panel, click Administrative Tools, and then double-click Event Viewer.

- Now you can follow any of the following steps.

1) When a log is full, it stops recording new events. Clearing the log is one way to free the log and start recording new events. To do so, on the Action menu (left click)or on the left side Application/System/Security (as available) right click and select Clear All events.

2) You can also free a log and start recording new events by overwriting old events. To overwrite events, on the Action menu, or on the left side Application/System/Security (as available) click Properties, and then click Overwrite events as needed. This ensures that all new events are written to the log, even when the log is full.

3) You can also start logging new events by increasing the maximum log size. To increase the log size, on the Action menu or on the left side Application/System/Security (as available) click Properties, and then increase the Maximum log size by typing a bigger value.